Evolution in Large Population

Question 1

Species need genetic diversity for:

Answer 1

1) Adaptive evolution
2) Evolutionary potential
Example, disease resistance and environmental change.

Question 2

Two ways to naturally regain lost genetic diversity.

Answer 2

Mutation

Migration

Question 3

Regaining genetic diversity

Answer 3

Large and small populations lose diversity by drift, this has more of an effect on small populations. Therefore, small pops must regain diversity. Rate of mutation, mutational load and migration need to be considered.

Question 4

Mutation

Answer 4

A sudden change in DNA base, chromosome number or arrangement or gene order. Can be deletion, substitution or insertion. Can be in a single base change or a block of DNA base sequence. Most mutations will decrease fitness (Californian Condors) although some may increase fitness (moths) and some are silent.

Question 5

Rates of mutation in quantitive characters

Answer 5

Muttions have a very slow rate. Quant characters are coded by many different loci, happen faster than mutations in a single loci. Mutations will accumulate in a population with time, rate of accumulation in a population is critical, can have important deleterious effects in inbred populations. Quant chars, mutations at many loci has a more rapid accumulation rate.

Question 6

Mutational load

Answer 6

Mutational load is the accumulated mutations that exist in a population at any one time. In small or declining populations mutational load becomes a problem. - Most mutations are recessive.
- Increased inbreeding means higher frequency of homozygotes.
-Deleterious effects become expressed in individuals.
Large populations can carry a larger mutational load because inbreeding is at a low freq.

Question 7

Selection and mutation

Answer 7

Mutations are random, they can appear in both non-function loci (where the effects will be neutral) and functional loci (Where effects will be deleterious). Selection will reduce the frequency of mutant allele but efficiency of selection will be dependent on the type of mutation. Lethal mutations intense selection. Example of Californian Condor. Selection in large populations takes longer to reduce the freq of the mutant allele.

Question 8

Mutation - Selection Balance

Answer 8

Equilibrium of elimination of deleterious mutations takes a long time and and the accumulation of new mutations over time. Net result is the mutational load.

Question 9

Effect of migration

Answer 9

• Addition or substitution of alleles from gene pool.
• Gene flow.
• Results in change in allele frequency over time.
• Can be extremely rapid.

Question 10

Migration and implications for conservation

Answer 10

-Gene flow between populations.
-Can aid small populations by adding diversity.
-Can threaten identity of small populations by genetic swapping.
Example, Ethiopian wolf hybrid with domestic dogs = Loss of local adaptations.

Question 11

Migration -Selection Equilibrium Summery

Answer 11

Migration and gene flow ensures homogeneity of allele frequency. When migration rate is high, effect of selection is weakened. Migration erases local adaptation. When migration is low selection is stronger, local adaptation returns.